The present invention relates to hand held electronic game units and particularly to such game units which include removable program cartridges.
Hand held electronic games are known which include a display screen, control switches and buttons and a microprocessor controller to control the various functions of the game when powered by a storage battery. The microprocessor controller may include a memory for storing a program to control the basic function of the microprocessor such as memory reading and writing and proper control of the display device which is frequently a Liquid Crystal display (LCD) panel. Known hand held video game units include an electrical connector by means of which memory containing program cartridges can be connected to the microprocessor. Replaceable cartridges -which generally store one application program in read only memory are thus used to add a new program, perhaps a video game, to the system.
When a cartridge is installed, its memory provides an additional program and data which becomes the application program of the device. Once a cartridge is installed, the program defined by the cartridge memory can be played repeatedly to the exclusion of other programs. When another program is to be run on the game unit, the prior cartridge is replaced with a new cartridge and a new program can be run until replaced. Although, such a system provides an almost unlimited number of programs which can be run one at a time, it does not allow multiple programs to be available in the unit at the same time. For example, it may be desirable to play a video game interactively over the internet. To do so requires a video game program and an internet access program. Such cannot be done on today's hand held video game units which provide only a single cartridge slot and thus the ability to run only one application program at a time. A need exists for a cartridge-based hand held electronic game unit which contemporaneously accommodates multiple cartridges for application programs.
Another problem which exists with known cartridge-based hand held game units is that the amount of memory available, even when the cartridge is present, is too limited due to the limited address spectrum of the control microprocessor. For example, when a game controller can access only 2 megabytes of memory the application program is limited to 2 megabytes minus the memory address spectrum portion needed for other parts of the hand held game operation. In order to increase the available memory, systems, such as that disclosed in U.S. Pat. No. 4,432,067 to Nielsen, have been proposed in which a cartridge of the system includes a plurality of groups of memory locations which in total comprise more memory than is available in the memory spectrum of the controller. Particular memory addresses are then used to select one or the other of the groups of memory locations in the single cartridge so that the particular group for access can be identified.
The Neilsen system has been found to provide some advantages but also to possess problems. For example, at least one extra access memory cycle is needed when memory group selection changes must be made. When frequent memory group changes are required, much memory access overhead may be incurred with the extra memory access cycles needed to switch between groups of locations. This slows down system operation. Also, the additional memory can be used only with the application program of the single cartridge and separate such systems require their own memory group switching capability. Even with expanded memory addressing capability, when the RAM provided in a cartridge fills with data no additional RAM can be provided. These shortcomings identify a problem and a need exists for an arrangement which is capable of providing additional memory for use by cartridge-contained application programs of a hand held video game.
It is also desirable for the hand held game to be able to identify the source of cartridges inserted into the system. Some cartridges, perhaps knock-off copies of proprietary cartridges, can then be denied access to hand held game units. Also, knowledge of the source of the game cartridge may permit the game controller to account for known incompatibilities. Thus, a further problem exists in marking, identifying and validating cartridges for hand held game units which is both accurate and secure.